I'm afraid she's getting to that age now that if she doesn't try soon, she's going to miss out.
Uhh...I think she is trying to tell you, "I don't want to play softball. I want to do something else."
Any ideas on how to get her to not be afraid?
Sure...you let her make decisions, and let her suffer the consequences of those decisions. When she finds out that she can live with her mistakes, she will not be afraid.
Teaching her how not to be afraid in this instance would be to explain the consequences of not playing, and let her do what she wants.
Missing a season of softball is not exactly the end of the world. Lots of kids live a rich, fulfiling life without ever playing softball.
So, I say let it go. If she starts to complain about not playing, say, "You made your decision. You can try out next year if you wish."
At what age would the transition from rec to TB be too hard?
Most kids can jump into TB at 14U. Going from rec to TB at 16U is almost impossible.